<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .active {
            color: red;
        }
    </style>
</head>
<body>
    <script src="../js/vue.js"></script>
    <div id ="app">
        <ul>
            <li :class="{active:currentIndex === index}" v-for="(book,index) in books" @click="btnClick(index)">{{index}}-{{book}}</li>
        </ul>
    </div>
    
    <script>
        let app = new Vue({
            el:"#app",
            data:{ 
                books: ["哈利波特","黑森林","十宗罪","钢铁是怎样练成的"
                ],
                currentIndex:''
            },
            methods(i){
                this.currentIndex = i
            }
        })
    </script>
</body>
</html>